1. Field of Invention
The current invention relates to EAS and RFID security tags and more particularly to methods of making UHF antennas for such tags and antennas made thereby.
2. Description of Related Art
RFID tags may be either active or passive. Active tags include their own on-board power, whereas passive use radio frequency signals from a transmitter to power the tag. When a passive tag receives the signal from the incident electromagnetic field, its antenna absorbs the energy received and directs it to an integrated circuit forming a part of the tag. The incident electromagnetic may contain data or instructions encoded into the signal. Using a portion of the energy received, the integrated circuit can then communicate back to a reader the details of data stored in the integrated circuit's on-board memory. The distance at which an RFID tag can be read/write depends on the output power of the RFID reader, the surrounding environment, and the efficiency with which the RFID tag interacts with the incident electromagnetic field. Thus, RFID tags are arranged to operate in various frequency bands, depending upon the application and the operating distance desired. One of those bands is the ultra high frequency (“UHF”) band of 850 MHz to 960 MHz. At present in the United States the UHF frequency for such tags is 915 MHz, in Europe it is 868 MHz and in Japan it is 956 MHz.
The manufacture or production of antennas for EAS and/or RFID tag applications on the most cost effective basis has been a desired goal of the industry for many years and the patent literature is replete with examples of systems and methods to produce antennas on a low cost basis. Examples of such patented systems/methods are found in: U.S. Pat. No. 3,497,410 (Zagusta et al.); U.S. Pat. No. 3,678,577 (Weglin et al.); U.S. Pat. No. 3,713,944 (Dennis); U.S. Pat. No. 4,495,232 (Bauser et al.); U.S. Pat. No. 4,846,922 (Benge et al.); U.S. Pat. No. 4,900,486 (Derakhshani et al.); U.S. Pat. No. 4,910,499 (Benge et al.); U.S. Pat. No. 4,954,818; (Benge et al.); U.S. Pat. No. 5,174,847 (Pichl); U.S. Pat. No. 5,362,374 (Chang); U.S. Pat. No. 5,645,932 (Uchibori); U.S. Pat. No. 5,829,121 (Shoemaker et al.); U.S. Pat. No. 5,759,422 (Schmelzer et al.); U.S. Pat. No. 5,899,144 (Parks); U.S. Pat. No. 6,214,444 (Uchibori); U.S. Pat. No. 6,383,616 (Uchibori); U.S. Pat. No. 6,458,465 (Uchibori); and U.S. Pat. No. 6,618,939 (Uchibori).
In U.S. Pat. No. 6,988,666 (Appalucci, et al.), entitled “Security Tag and Process for Making Same” which is assigned to the same assignee as this invention and whose disclosure is incorporated by reference herein there is disclosed and claimed a method for producing security tags and components therefor, e.g., coil antennas for HF (high frequency) security tags, on a low cost basis. While the antenna making methods disclosed in this patent are suitable for their intended purposes, those methods are based on applying a patterned adhesive in the shape of the desired component, e.g., the coil antenna, onto a substrate and then die cutting around that pattern. Such action leaves something to be desired from the standpoint of manufacturing simplicity and cost, particularly where the antennas to be created are significantly thinner and simpler in geometry.
As is known UHF antennas can be made as thin as approximately 5 microns, since such antennas operate on the skin effect. Moreover, UHF antennas are typically somewhat simpler in geometry than coil antennas used in HF tags. Accordingly, the techniques of U.S. Pat. No. 6,988,666 (Appalucci et al.) may not be the most cost effective methods for the production of very thin UHF antennas.
Thus, a need exists for a method of producing very thin, UHF antennas for tags on a very low cost basis.
The subject invention addresses that need by making use of some low cost practices and techniques implemented in the label making/converting industry.